Aluminum alloys



Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE Aluminum Company ofAmerica, Pittsburgh,

Pa., a corporation of Pennsylvania No Drawing. Original applicationSeptember 21, 1932, Serial No. 634,155. Divided and this applicationNovember 30, 1932. Serial No.

1 Claim.

This invention relates to aluminum base alloys containing magnesium. Theinvention has for its object the improvement of alloys of this class bythe addition thereto of about 0.05 to 2.0 per cent by weight of calcium.The invention is particularly concerned with the specific alloyshereinafter described.

The claim of this application covers certain matter divided from mycopending application Serial No. 634,155 which is, in part, acontinuation of my copending application Serial No. 595,231. Inventionsdisclosed but not claimed herein are claimed in my copendingapplications Serial Nos. 595,231, filed February 25, 1932, 645,- 108 to645,110 inclusive, and 645,112 to 645,125 inclusive, all filed November20, 1932.

Considerable difliculty has heretofore been encountered in attempts tocommercially produce castings of aluminum base alloys containingsubstantial amounts of magnesium. This diihculty is encountered both inthe making of sand castings and permanent moldor chill-mold castings,although the nature of the difliculty difiers somewhat in each case. Inthe case of sand castings there occurs a reaction between the a moltenaluminum base alloy containing magnesium and the ordinary sand-moldmaterials, or vapors generated therefrom. There is also a reaction withthe atmosphere. In addition, the magnesium-containing aluminum basealloy does not flow freely through narrow mold sections at ordinarypouring temperatures and, if the pouring temperature be raised, thesolidified alloy is unsound. If the aluminum base alloy containingmagnesium be cast in a chill-mold the reaction effect is minimized tosome extent, but the troubles arising from cold-shuts and miss-runs areaccentuated because of the more rapid chilling of the molten metal. Theconsiderations apply to the aluminum base alloys specifically disclosedherein and particularly to such alloys.

I have discovered that when calcium is added to aluminum base alloys ofthe type and composition herein described, these difliculties are, to aconsiderable extent, eliminated. The calcium should be present inamounts ranging from 0.05 per cent to 2.0 per cent by weight subject tospecific considerations as hereinafter disclosed.

In the melting of aluminum alloys of the compositions herein described,a viscous scum often forms at the surface of the molten metal. Failureof the molten metal to run properly through narrow mold apertures iscaused, in part, by shreds or particles of this scum being suspended inthe molten metal and ofiering a resistance to the free passage of themetal through the apertures. Regardless of the cause of this lowfluidity, I have discovered that the addition to the alloy of relativelysmall amounts of calcium, in the preferred range between 0.05 to 0.5 percent. improves the casting characteristics to a very considerable extentand simultaneously effects a reduction of the scum or dross collectingat or near the surface. In the casting of articles in sand molds, Iprefer to add calcium in amounts less than about 0.5 per cent except ininstances where some reduction of tensile strength or other mechanicalor tensile property is immaterial. In amounts of more than 0.5 per centthe calcium addition produces the advantages enumerated herein but has atendency to lower some of the physical properties of the alloys. Thisefiect is not harmful when calcium is present in amounts of about 0.5per cent or less, but when high strength is not a desideratum thecalcium may be used in amounts up to about 2.0 per cent. In intricatepermanent mold castings, where casting troubles are very serious if nocalcium be added, the improved physical properties obtained coincidentwith the production of good castings more than ofiset the diminution inproperties which might otherwise result from the use of the calcium.

I have also discovered that when calcium is added to aluminum basealloys containing magnesium, the amount of gas evolved duringsolidificationpf the alloys is considerably reduced. When from about0.05 per cent to 2.0 per cent by weight of calcium is added to thealloys, the amount of gas evolved becomes less marked with increasingcalcium content and the reduction of gas evolution may be so marked thatthe molten metal cools to the solidification temperature with a smoothmirror-like surface. I prefer to restrict the amount of calcium added to2.0 per cent or less since above this amount the physical properties ofthe alloys may be too seriously afiected. If the best physicalproperties are desired with an improved, although not complete, degreeof gas prevention, I keep the calcium content of the alloys between 0.05per cent and about 0.5 per cent.

In the application of the principles of my invention I have determinedthat certain aluminum base alloys containing magnesium are particularlybenefited thereby. For example, a very useful aluminum base alloy is onecontaining about 2.0 to-9.0 per cent of magnesium and 0.05

per cent to 2.0 per cent of calcium, as is also aluminum base alloycontaining about 2.0 to 15.0 per cent of magnesium, 0.1 to 3.5 per centof cobalt, and 0.05 to 2.0 per cent of calcium to which other elementssuch as copper, antimony, bismuth, nickel, manganese, and other wellknown alloying elements may be added to produce particular propertiestherein.

Likewise is the addition of 0.05 to 2.0 per cent of calcium beneficialto those aluminum base alloys which contain about 2.0 to 15.0 per centof magnesium and 0.05 to 0.4 per cent of at least one of the class ofmetals here defined as antimony and bismuth, such alloys being veryuseful where use at high temperatures is contemplated. Calcium maylikewise be added to improve such alloys when they contain, in additionto magnesium and antimony and/or bismuth, one or more of such alloyingelements as cobalt, copper, nickel, manganese, zinc, etc. which may beadded to modify or produce a specific property in the alloy.

The addition of 0.05 to 2.0 per cent of calcium is very beneficial inthecase of'a series of aluminum base alloys which contain as major alloyingelements about 2.0 to 10.0 per cent of magnesium and about 0.2 to 5.0per cent of nickel. For instance, an aluminum base alloy containing 3.0to 7.5 per cent of magnesium and 0.2 to 2.0 per cent of nickel isimproved by the addition of 0.05 to 2.0 per cent of calcium as is,likewise, this same alloy when it also contains about 0.05 to 0.4 percent of one or more of the class of elements composed of antimony andbismuth. Another excellent aluminum base alloy prepared in accordancewith the principles of my invention is one containing 3.0 to 8.0 percent of magnesium, 0.5 to 4.0 per cent of nickel, 0.5 to 4.0 per cent ofmanganese, and 0.05 to 2.0 per cent of calcium, which alloy may also beimproved, particularly for application at high temperatures, by theaddition of 0.05 to 0.4 per cent of at least one of the class ofelements composed of antimony and bismuth.

The principles of my invention find particular application in the caseof aluminum base alloys containing magnesium nickel, andchromium,-andaluminiumbasealloyscontainingmag% nesium, nickel, andcopper, as well as those alloys containing mag-nesium, nickel, andcobalt. Examples may be given of aluminum base alloys containing 2.0 to10.0 per cent of magnesium, 0.2 to 5.0 per cent of nickel, 0.5 to 3.5per cent of chromium, and 0.05 to 2.0 per cent of calcium. An aluminumbase alloy containing 3.0 to 8.0 per cent of magnesium, 0.5 to 3.5 percent of nickel, 0.5 to 3.5 per cent of chromium, and 0.05 to 2.0 percent of calcium has excellent casting properties and the hightemperature properties of this alloy can be favorably affected by theaddition of 0.05 to 0.4 per cent of at least one of a class of elementscomposed of bismuth and antimony. Examples may be given of aluminum basealloy containing 2.0v

to 10.0 per cent of magnesium, 0.2 to 5.0 per cent of nickel, 1.0 to 6.0per cent of copper, and 0.05

to 2.0 per cent of calcium. An excellent alloy of this type is onecontaining 3.0 to 8.0 per cent ofmagnesium, 0.5 to 5.0 per cent ofnickel,

1.0 to 6.0 per cent of copper, and 0.05 to 2.0 per cent of calcium withor without 0.05 to 0.4 per cent of at least one of the class of elementscomposed of antimony and bismuth and with or without the furtheraddition of 0.5 to 3.5 per cent of at least one of a class of elementscomposed of cobalt and chromium, and with or without the furtheraddition of 0.1 to 1.0 per cent of at least one of a class of elementscomposed of tungsten, vanadium, molybdenum, titanium, andzirconium.

Other excellent alloys are those aluminum base alloys containing about2.0 to 10.0 per cent magnesium, 0.2 to 5.0 per cent nickel, 0.1 to 3.5per cent cobalt, and 0.05 to 2.0 per cent of calcium. A particularexample of this class of alloys, which may also contain withconsiderable advantage 0.05 to 0.4 per cent of a class of elementscomposed of antimony and bismuth, is the aluminum base alloy containing3.0 to 8.0 per cent magnesium, 0.5 to 4.0 per cent nickel,

0.1 to 3.0 per cent cobalt, and 0.05 to 2.0 per cent calcium.

Among other magnesium-containing aluminum base alloys which I have foundto be particularly benefited by the presence of calcium are numbered thealuminum base alloys containing 3.0 to 8.0 per cent of magnesium, 1.0 to6.0 per cent of copper, 0.5 to 3.5 per cent of chro-' mium, and 0.05 to2.0 per cent of calcium, with or without the addition of 0.05 to 0.4 percent of at least one of a class of metals composed of antimony andbismuth and with or without the addition of other alloying elements.

The alloys herein described may be produced by the usual methods ofalloying metals. The calcium is preferably added to the molten alloy bythrusting the calcium beneath the surface v with tongs or other suitableinstrument. The aluminum used in preparing the alloys may be pure or itmay contain the impurities found in commercial grades of this metal.Ordinarily a good commercial grade of Virgin aluminum will giveexcellent results and is preferable.

Having thus explained and described my invention, I claim:

A metallic alloy consisting of 3.0 to 8.0 per cent by weight ofmagnesium, 0.5 to 4.0 per cent by weight of nickel, 0.5 to 4.0 per centby weight of manganese, 0.05 to 2.0 per cent by weight of calcium, and0.05 to 0.4 per cent by weight of at least one of a class of elementscomposed of antimony and bismuth, the balance being aluminum.

ROBERT T. WOOD.

